Liquid-ejecting head, liquid-ejecting apparatus, piezoelectric element, and piezoelectric material

ABSTRACT

A liquid-ejecting head includes a pressure-generating chamber communicating with a nozzle opening, and a piezoelectric element. The piezoelectric layer contains a perovskite complex oxide containing Bi, La, Fe, and Mn and is ferroelectric.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.12/914,233 filed Oct. 28, 2010 (which patent application is incorporatedherein by reference in its entirety). U.S. patent application Ser. No.12/914,233 claims the benefit of Japanese Patent Application No.2009-252445 filed Nov. 2, 2009 (which is expressly incorporated hereinby reference in its entirety), Japanese Patent Application No.2010-052430 filed Mar. 9, 2010 (which also is expressly incorporatedherein by reference in its entirety), and Japanese Patent ApplicationNo. 2010-115744 filed May 19, 2010 (which is also expressly incorporatedherein by reference in its entirety).

BACKGROUND

1. Technical Field

The present invention relates to a liquid-ejecting head that includes apiezoelectric element, a liquid-ejecting apparatus, the piezoelectricelement, and a piezoelectric material. The piezoelectric elementincludes a first electrode for altering the internal pressure of apressure-generating chamber communicating with a nozzle opening, apiezoelectric layer, and a second electrode.

2. Related Art

One example of piezoelectric elements for use in liquid-ejecting headsis a piezoelectric layer between two electrodes. The piezoelectric layeris formed of a piezoelectric material having an electromechanicaltransfer function, such as a crystallized dielectric material. Such apiezoelectric element can be mounted on a liquid-ejecting head as anactuator in a flexural vibration mode. One representative example ofliquid-ejecting heads is an ink jet print head. The ink jet print headhas a diaphragm as part of a pressure-generating chamber, whichcommunicates with a nozzle opening for discharging ink droplets. Thediaphragm is deformed by a piezoelectric element to pressurize ink inthe pressure-generating chamber, thereby discharging ink droplets fromthe nozzle opening. A piezoelectric element for use in such an ink jetprint head can be produced by forming a uniform piezoelectric layer onthe entire surface of a diaphragm by a film-forming technique anddividing the piezoelectric layer by lithography into piecescorresponding to each individual pressure-generating chamber.

The piezoelectric material used for such a piezoelectric elementrequires excellent piezoelectric characteristics (a large strain). Onerepresentative example of the piezoelectric material is lead zirconiumtitanate (PZT) (see JP-A-2001-223404). PZT is a ferroelectric substance.In ferroelectric substances, spontaneous polarization occursunidirectionally, and the piezoelectric strain increases linearly withvoltage applied. This facilitates the control of piezoelectric strainand the size of droplets discharged. Thus, PZT is suitable for use inactuators.

However, from the standpoint of environmental protection, there is ademand for a piezoelectric material with little or no lead. Theseproblems are not confined to liquid-ejecting heads, including ink jetprint heads, and occur in other piezoelectric elements.

SUMMARY

An advantage of some aspects of the invention is that it provides aliquid-ejecting head that includes a piezoelectric element formed of aferroelectric substance and having a low environmental load, aliquid-ejecting apparatus, the piezoelectric element, and apiezoelectric material.

In accordance with one aspect of the invention, a liquid-ejecting headincludes a pressure-generating chamber communicating with a nozzleopening, and a piezoelectric element that includes a first electrode, apiezoelectric layer disposed on the first electrode, and a secondelectrode disposed on the piezoelectric layer, wherein the piezoelectriclayer contains a perovskite complex oxide containing Bi, La, Fe, and Mnand is ferroelectric.

Use of a piezoelectric material that contains a perovskite complex oxidecontaining Bi, La, Fe, and Mn and is ferroelectric can reduce the leadcontent and the environmental load and facilitates the control ofpiezoelectric strain. Thus, the liquid-ejecting head can include apiezoelectric element in which it is easy to control the size ofdroplets discharged.

In accordance with another aspect of the invention, a liquid-ejectinghead includes a pressure-generating chamber communicating with a nozzleopening, and a piezoelectric element that includes a first electrode, apiezoelectric layer disposed on the first electrode, and a secondelectrode disposed on the piezoelectric layer, wherein the piezoelectriclayer contains a complex oxide having the following general formula (1).The complex oxide having the following general formula (1) is aferroelectric substance. Use of such a ferroelectric substance canreduce the lead content and the environmental load and facilitate thecontrol of piezoelectric strain.(Bi_(1−x),La_(x))(Fe_(1−y),Mn_(y))O₃  (1)

-   -   (0.10≦x≦0.20, 0.01≦y≦0.09)

In the general formula (1), x is preferably in the range of 0.17≦x≦0.20,more preferably 0.19≦x≦0.20. Such a composition has both anantiferroelectric phase and a ferroelectric phase. Thus, thepiezoelectric element can produce a large strain.

In the general formula (1), y is preferably in the range of 0.01≦y≦0.05.In this range, the piezoelectric layer has excellent insulatingproperties and can prevent dielectric breakdown of the liquid-ejectinghead caused by an electric leakage.

Preferably, the piezoelectric layer has an X-ray diffraction patternthat includes both a diffraction peak assigned to a ferroelectric phaseand a diffraction peak assigned to an antiferroelectric phase. Acombination of an antiferroelectric phase and a ferroelectric phase canprovide a piezoelectric element that can produce a large strain.

Preferably, the piezoelectric layer has an X-ray diffraction patternthat includes a diffraction peak of an ABO₃ structure at 45°<2θ<50°, andthe diffraction peak of the ABO₃ structure has an A_(AF)/A_(F) ratio of0.1 or more. A_(F) denotes the area intensity of a diffraction peakassigned to a ferroelectric phase, and A_(AF) denotes the area intensityof a diffraction peak assigned to an antiferroelectric phase. Thisinsures that the piezoelectric element can produce a large strain.

In accordance with another aspect of the invention, a liquid-ejectingapparatus includes a liquid-ejecting head according to any of theaspects described above. Use of such a liquid-ejecting head can reducethe lead content and the environmental load. In addition, theliquid-ejecting head includes a piezoelectric element that allows thepiezoelectric strain to be easily controlled. Thus, the liquid-ejectingapparatus including the liquid-ejecting head has excellent dischargecharacteristics without adversely affecting the environment.

In accordance with still another aspect of the invention, apiezoelectric element includes a piezoelectric layer and a plurality ofelectrodes disposed on the piezoelectric layer, wherein thepiezoelectric layer contains a perovskite complex oxide containing Bi,La, Fe, and Mn and is ferroelectric. Use of a piezoelectric materialthat contains a perovskite complex oxide containing Bi, La, Fe, and Mnand is ferroelectric can reduce the lead content and the environmentalload and facilitates the control of piezoelectric strain.

In accordance with still another aspect of the invention, apiezoelectric element includes a piezoelectric layer and a plurality ofelectrodes disposed on the piezoelectric layer, wherein thepiezoelectric layer contains a complex oxide having the followinggeneral formula (1). The complex oxide having the following generalformula (1) is a ferroelectric substance. Use of such a ferroelectricsubstance can reduce the lead content and the environmental load andfacilitate the control of piezoelectric strain.(Bi_(1−x),La_(x))(Fe_(1−y),Mn_(y))O₃  (1)

-   -   (0.10≦x≦0.20, 0.01≦y≦0.09)

In accordance with still another aspect of the invention, apiezoelectric material contains a perovskite complex oxide containingBi, La, Fe, and Mn and is ferroelectric. The piezoelectric material canreduce the lead content and the environmental load and facilitate thecontrol of piezoelectric strain.

In accordance with still another aspect of the invention, apiezoelectric material contains a perovskite complex oxide having thefollowing general formula (1). The perovskite complex oxide having thefollowing general formula (1) is a ferroelectric substance. Use of sucha ferroelectric substance can reduce the lead content and theenvironmental load and facilitate the control of piezoelectric strain.(Bi_(1−x),La_(x))(Fe_(1−y),Mn_(y))O₃  (1)

-   -   (0.10≦x≦0.20, 0.01≦y≦0.09)

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a schematic exploded perspective view of a print headaccording to a first embodiment.

FIG. 2A is a plan view of the print head according to the firstembodiment.

FIG. 2B is a cross-sectional view of the print head taken along the lineIIB-IIB of FIG. 2A.

FIG. 3 is a graph showing a P-V curve according to Example 1.

FIG. 4 is a graph showing a P-V curve according to Example 2.

FIG. 5 is a graph showing a P-V curve according to Example 3.

FIG. 6 is a graph showing a P-V curve according to Example 4.

FIG. 7 is a graph showing a P-V curve according to Example 5.

FIG. 8 is a graph showing a P-V curve according to Example 6

FIG. 9 is a graph showing a P-V curve according to Example 7.

FIG. 10 is a graph showing a P-V curve according to Example 8.

FIG. 11 is a graph showing a P-V curve according to Example 9.

FIG. 12 is a graph showing a P-V curve according to Example 10.

FIG. 13 is a graph showing a P-V curve according to Example 11.

FIG. 14 is a graph showing a P-V curve according to Comparative Example1.

FIG. 15 is a graph showing a P-V curve according to Comparative Example2.

FIG. 16 is a graph showing a P-V curve according to Comparative Example3.

FIG. 17 is a graph showing a P-V curve according to Comparative Example4.

FIG. 18 is a graph showing an X-ray diffraction pattern according toTest Example 2.

FIG. 19 is a graph showing a principal part of an X-ray diffractionpattern according to Test Example 2.

FIG. 20 is a graph showing an X-ray diffraction pattern according toTest Example 2.

FIG. 21 is a graph showing an S-V curve according to Example 4.

FIG. 22 is a graph showing an S-V curve according to Example 11.

FIG. 23 is a graph showing an S-V curve according to Comparative Example3.

FIG. 24 is a graph showing an S-V curve according to Example 5.

FIG. 25 is a graph showing an S-V curve according to Example 6.

FIG. 26 is a graph showing an S-V curve according to Example 9.

FIG. 27 is a schematic view of a printer according to one embodiment ofthe invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

First Embodiment

FIG. 1 is an exploded perspective view of an ink jet print headaccording to a first embodiment of the invention. This ink jet printhead is an example of a liquid-ejecting head. FIG. 2A is a plan view ofthe ink jet print head according to the first embodiment. FIG. 2B is across-sectional view of the ink jet print head taken along the lineIIB-IIB of FIG. 2A.

As illustrated in FIGS. 1 and 2, a flow-passage-forming substrate 10according to the present embodiment is a silicon single crystalsubstrate. A silicon dioxide elastic film 50 is disposed on theflow-passage-forming substrate 10.

The flow-passage-forming substrate 10 includes a plurality ofpressure-generating chambers 12 juxtaposed to each other in the widthdirection. The flow-passage-forming substrate 10 further includes acommunication portion 13 outside the pressure-generating chambers 12 inthe longitudinal direction. The communication portion 13 is incommunication with the pressure-generating chambers 12 throughcorresponding ink feed channels 14 and communication paths 15. Thecommunication portion 13 in communication with a reservoir portion 31 ina protective substrate described below constitutes part of a reservoir,which is a common ink chamber of the pressure-generating chambers 12.The ink feed channels 14 have a smaller width than thepressure-generating chambers 12, producing a constant flow resistanceagainst ink flowing from the communication portion 13 to thepressure-generating chambers 12. While each of the flow passages isnarrowed at one side thereof in the present embodiment, each of the flowpassages may be narrowed at both sides thereof to form the ink feedchannels 14. Alternatively, instead of reducing the width of the flowpassages, the thickness of the flow passages may be reduced to form theink feed channels 14. Thus, the flow-passage-forming substrate 10includes liquid flow passages, which are composed of thepressure-generating chambers 12, the communication portion 13, the inkfeed channels 14, and the communication paths 15.

The opening surface of the flow-passage-forming substrate 10 is attachedto a nozzle plate 20 with an adhesive, a heat-seal film, or the like.The nozzle plate 20 has nozzle openings 21 near the ends of thepressure-generating chambers 12 opposite the ink feed channels 14. Thenozzle plate 20 is formed of glass ceramic, a silicon single crystal, orstainless steel, for example.

As described above, the elastic film 50 is disposed opposite the openingsurface of the flow-passage-forming substrate 10. An insulator film 55formed of, for example, zirconium oxide is formed on the elastic film50.

A piezoelectric element 300 is disposed on the insulator film 55 andincludes a first electrode 60, a piezoelectric layer 70, and a secondelectrode 80. The piezoelectric layer 70 has a thickness of 2 μm orless, preferably in the range of 0.3 to 1.5 μm. A titanium oxide layermay be disposed between the piezoelectric element 300 and the insulatorfilm 55 to improve the adhesion therebetween. In general, one of theelectrodes of the piezoelectric element 300 serves as a commonelectrode, and the other electrode and the piezoelectric layer 70 arepatterned for each of the pressure-generating chambers 12. In thepresent embodiment, the first electrode 60 serves as the commonelectrode of the piezoelectric elements 300 and the second electrode 80serves as an individual electrode of the corresponding piezoelectricelement 300. However, for the convenience of a drive circuit or wiring,the first electrode 60 may serve as the individual electrode and thesecond electrode 80 may serve as the common electrode. A combination ofa piezoelectric element 300 and a diaphragm is herein referred to as anactuator. The diaphragm can be deformed by the operation of thepiezoelectric element 300. Although the elastic film 50, the insulatorfilm 55, and the first electrode 60 function as the diaphragm in thepresent embodiment, the diaphragm is not limited to this structure. Forexample, the first electrode 60 alone may function as the diaphragm.Alternatively, the piezoelectric element 300 may function as thediaphragm.

The piezoelectric layer 70 is formed of a perovskite complex oxidecontaining Bi, La, Fe, and Mn and is ferroelectric. More specifically,for example, the piezoelectric layer 70 is formed of an ABO₃ complexoxide having the following general formula (1). As shown in the examplesdescribed below, the ABO₃ complex oxide having the following generalformula (1) is a ferroelectric substance.(Bi_(1−x),La_(x))(Fe_(1−y),Mn_(y))O₃  (1)

-   -   (0.10≦x≦0.20, 0.01≦y≦0.09)

In the perovskite ABO₃ structure, the A sites have oxygen atoms in12-fold coordination, and the B sites have oxygen atoms in 6-foldcoordination, forming an octahedron. Bi and La are located at the Asites, and Fe and Mn are located at the B sites.

Use of such a ferroelectric ABO₃ complex oxide containing Bi, La, Fe,and Mn in the piezoelectric layer can reduce the lead content and theenvironmental load and facilitate the control of piezoelectric strainand the control of ink droplet size. As shown in the examples andcomparative examples described below, depending on the composition, theABO₃ complex oxide containing Bi, La, Fe, and Mn may be a ferroelectricsubstance or an antiferroelectric substance.

An antiferroelectric substance includes adjacent dipoles oriented inantiparallel directions and can undergo electric-field-induced phasetransition above a certain voltage. A piezoelectric layer formed of suchan antiferroelectric substance can produce a larger strain than apiezoelectric layer formed of a ferroelectric substance. However, thepiezoelectric layer formed of an antiferroelectric substance cannot bedriven below a certain voltage. In addition, the piezoelectric straindoes not change linearly with voltage. The term “electric-field-inducedphase transition” means phase transition induced by an electric fieldand includes phase transition from an antiferroelectric phase to aferroelectric phase and phase transition from a ferroelectric phase toan antiferroelectric phase. The term “ferroelectric phase” means thatspontaneous polarization occurs unidirectionally. The term“antiferroelectric phase” means that adjacent dipoles are oriented inantiparallel directions. For example, in phase transition from anantiferroelectric phase to a ferroelectric phase, some adjacent dipolesoriented in antiparallel directions in the antiferroelectric phase areinverted such that the dipoles are oriented unidirectionally. Suchelectric-field-induced phase transition expands or contracts lattices toproduce a strain (electric-field-induced phase transition strain). Asubstance that can undergo electric-field-induced phase transition is anantiferroelectric substance. Thus, in an antiferroelectric substance,some adjacent dipoles oriented in antiparallel directions in the absenceof an electric field are inverted such that the dipoles are orientedunidirectionally upon the application of an electric field. In a P-Vcurve showing the amount of polarization P of an antiferroelectricsubstance as a function of voltage V, the antiferroelectric substancehas double hysteresis loops in the positive electric field direction andthe negative electric field direction. In regions where the amount ofpolarization changes drastically, there is phase transition from aferroelectric phase to an antiferroelectric phase and from anantiferroelectric phase to a ferroelectric phase.

Unlike the antiferroelectric substance, a ferroelectric substance doesnot have a double hysteresis in a P-V curve. In the ferroelectricsubstance, spontaneous polarization occurs unidirectionally, and thepiezoelectric strain increases linearly with voltage applied. Thus, theferroelectric substance facilitates the control of piezoelectric strainand the control of droplet size, and a single piezoelectric element cangenerate both a small amplitude vibration (microvibration) and a largeamplitude vibration, which generates a large excluded volume.

In the X-ray diffraction measurement of the piezoelectric layer 70, thediffraction pattern preferably includes both a diffraction peak assignedto a ferroelectric phase and a diffraction peak assigned to anantiferroelectric phase. More preferably, the X-ray diffraction patternincludes a diffraction peak of an ABO₃ structure at 45°<2θ<50°, and thediffraction peak of the ABO₃ structure has an A_(AF)/A_(F) ratio of 0.1or more. A_(F) denotes the area intensity of a diffraction peak assignedto a ferroelectric phase, and A_(AF) denotes the area intensity of adiffraction peak assigned to an antiferroelectric phase. Thepiezoelectric layer 70 that includes both a diffraction peak assigned toa ferroelectric phase and a diffraction peak assigned to anantiferroelectric phase, that is, the piezoelectric layer 70 thatincludes a morphotropic phase boundary (MPB) between theantiferroelectric phase and the ferroelectric phase can provide apiezoelectric element that can produce a large strain.

In the piezoelectric layer 70, x is preferably in the range of0.17≦x≦0.20, more preferably 0.19≦x≦0.20, in the general formula (1). Inthese ranges, as shown in the examples described below, the X-raydiffraction pattern includes both a diffraction peak assigned to aferroelectric phase and a diffraction peak assigned to anantiferroelectric phase, showing the coexistence of theantiferroelectric phase and the ferroelectric phase. The MPB between theantiferroelectric phase and the ferroelectric phase can provide apiezoelectric element that can produce a large strain. When y is in therange of 0.01≦y≦0.05, the piezoelectric layer 70 also has high leakageresistance.

The piezoelectric element 300 can be formed on the flow-passage-formingsubstrate 10 by any method, including the following method. First, asilicon dioxide (SiO₂) film is formed as the elastic film 50 on asilicon wafer used as the flow-passage-forming substrate 10. A zirconiumoxide insulator film 55 is then formed on the elastic film 50 (silicondioxide film).

If necessary, a titanium oxide layer is formed on the insulator film 55.A platinum or iridium first electrode 60 is then formed on the entiresurface by sputtering and is patterned.

A piezoelectric layer 70 is then formed on the first electrode 60. Thepiezoelectric layer 70 may be formed by any method, includingmetal-organic decomposition (MOD). In MOD, an organometallic compounddissolved or dispersed in a solvent is applied to the first electrode60, is dried, and is fired at a high temperature to form thepiezoelectric layer 70 formed of a metal oxide. The piezoelectric layer70 may also be formed by a sol-gel method, laser ablation, sputtering,pulse laser deposition (PLD), CVD, or aerosol deposition.

For example, a sol or MOD solution (precursor solution) that contains anorganometallic compound, more specifically, an organometallic compoundcontaining bismuth, lanthanum, iron, and manganese at a predeterminedratio is applied to the first electrode 60 by spin coating to form apiezoelectric precursor film (a coating step).

The precursor solution is prepared by mixing organometallic compoundscontaining bismuth, lanthanum, iron, or manganese such that the metalsare contained at a desired molar ratio, and dissolving or dispersing themixture in an organic solvent, such as an alcohol. Examples of theorganometallic compounds containing bismuth, lanthanum, iron, ormanganese include metal alkoxides, organic acid salts, and β-diketonecomplexes. One example of the organometallic compound containing bismuthis bismuth 2-ethylhexanoate. An exemplary organometallic compoundcontaining lanthanum is lanthanum 2-ethylhexanoate. An exemplaryorganometallic compound containing iron is iron 2-ethylhexanoate. Anexemplary organometallic compound containing manganese is manganese2-ethylhexanoate.

The piezoelectric precursor film is then heated at a predeterminedtemperature for a predetermined period of time for drying (a dryingstep). The dried piezoelectric precursor film is then heated at apredetermined temperature for a predetermined period of time fordegreasing (a degreasing step). The term “degreasing”, as used herein,means that organic components contained in the piezoelectric precursorfilm are removed as NO₂, CO₂, and/or H₂O, for example.

The piezoelectric precursor film is then heated at a predeterminedtemperature, for example, approximately in the range of 600° C. to 700°C., for a predetermined period of time to form a piezoelectric film bycrystallization (a sintering step). Examples of a heater used in thedrying step, the degreasing step, and the sintering step include a hotplate and a rapid thermal annealing (RTA) apparatus. RTA involvesheating by infrared lamp irradiation.

Depending on the desired film thickness, the coating step, the dryingstep, the degreasing step, and optionally the sintering step may beperformed more than once to form a piezoelectric layer composed of aplurality of piezoelectric films.

After the formation of the piezoelectric layer 70, a second electrode80, for example, formed of a metal, such as platinum, is formed on thepiezoelectric layer 70. The piezoelectric layer 70 and the secondelectrode 80 are then simultaneously patterned to form the piezoelectricelement 300.

If necessary, the piezoelectric element 300 may be post-annealed at atemperature in the range of 600° C. to 700° C. Post-annealing canprovide a good interface between the piezoelectric layer 70 and thefirst electrode 60 or the second electrode 80 and improve thecrystallinity of the piezoelectric layer 70.

EXAMPLES

The invention will be further described in the following examples.However, the invention is not limited to these examples.

Example 1

A silicon dioxide film having a thickness of 400 nm was formed on a(100)-oriented silicon substrate by thermal oxidation. A titanium filmhaving a thickness of 40 nm was formed on the silicon dioxide film by RFsputtering and was then thermally oxidized to form a titanium oxidefilm. A platinum film having a thickness of 150 nm was formed on thetitanium oxide film by ion sputtering and vapor deposition to form a(111)-oriented first electrode 60.

A piezoelectric layer was formed on the first electrode 60 by spincoating in the following manner. First, solutions of bismuth2-ethylhexanoate, lanthanum 2-ethylhexanoate, iron 2-ethylhexanoate, ormanganese 2-ethylhexanoate in xylene and octane were mixed at apredetermined ratio to prepare a precursor solution. The precursorsolution was dropped on the substrate on which the titanium oxide filmand the first electrode were formed, and the substrate was rotated at1500 rpm to form a piezoelectric precursor film (a coating step). Dryingand degreasing were then performed at 350° C. for 3 minutes (a dryingand degreasing step). After the coating step and the drying anddegreasing step were performed three times, sintering was performed byrapid thermal annealing (RTA) at 650° C. for 1 minute (a sinteringstep). The three cycles of the coating step and the drying anddegreasing step and the single sintering step were performed four times(12 coating steps in total). Sintering by RTA at 650° C. for 10 minutesyielded a piezoelectric layer 70 having a thickness of 350 nm.

A platinum film having a thickness of 100 nm was formed by DC sputteringas a second electrode 80 on the piezoelectric layer 70. Sintering by RTAat 650° C. for 10 minutes yielded a piezoelectric element 300. Thepiezoelectric element 300 included the piezoelectric layer 70 formed ofan ABO₃ complex oxide having the general formula (1) in which x=0.10 andy=0.03.

Examples 2 to 11 and Comparative Examples 1 to 7

Piezoelectric elements 300 were formed in the same way as in Example 1except that solutions of bismuth 2-ethylhexanoate, lanthanum2-ethylhexanoate, iron 2-ethylhexanoate, or manganese 2-ethylhexanoatein xylene and octane were mixed at different ratios to formpiezoelectric layers 70 formed of complex oxides having the generalformula (1) in which x and y were shown in Table 1. In Examples 5, 6,and 9, a silicon dioxide film having a thickness of 1030 nm was formedon a (110)-oriented silicon substrate by thermal oxidation. A zirconiumoxide layer having a thickness of 400 nm, a titanium layer having athickness of 20 nm, and a platinum layer having a thickness of 130 nmwere stacked on the silicon dioxide film by DC sputtering to form a(111)-oriented platinum electrode. The orientation of the substrate andthe presence of the titanium oxide film did not affect thecharacteristics of the piezoelectric layer 70.

TABLE 1 x y Example 1 0.10 0.03 Example 2 0.10 0.05 Example 3 0.10 0.09Example 4 0.14 0.05 Example 5 0.17 0.03 Example 6 0.18 0.03 Example 70.20 0.01 Example 8 0.20 0.02 Example 9 0.19 0.03 Example 10 0.19 0.04Example 11 0.19 0.05 Comparative Example 1 0.21 0.03 Comparative Example2 0.24 0.05 Comparative Example 3 0.29 0.05 Comparative Example 4 0.480.05 Comparative Example 5 0.20 0.00 Comparative Example 6 0.10 0.00Comparative Example 7 0.00 0.00

Test Example 1

The relationship between the amount of polarization (P) and voltage (V)for the piezoelectric elements 300 according to Examples 1 to 11 andComparative Examples 1 to 7 was determined using a 25- or 30-Vtriangular wave at a frequency of 1 kHz in a ferroelectric test system“FCE-1A” manufactured by Toyo Co. using an electrode pattern of φ=400μm. FIGS. 3 to 17 show the results. Comparative Examples 5 to 7 had toomuch leakage to determine the relationship and could not be used aspiezoelectric materials.

FIGS. 3 to 13 shows that Examples 1 to 11 had a hysteresis loopcharacteristic of a ferroelectric substance. Thus, in Examples 1 to 11,the piezoelectric strain increases linearly with voltage applied and iseasy to control.

As shown in FIGS. 14 to 16, Comparative Examples 1 to 3, which had x andy outside the ranges of 0.10≦x≦0.20 and 0.01≦y≦0.09 in the generalformula (1), were antiferroelectric substances having double hysteresischaracteristic of an antiferroelectric substance in the positiveelectric field direction and the negative electric field direction. Asshown in FIG. 17, Comparative Example 4 was a paraelectric material.Comparative Examples 5 to 7 could not be used as a piezoelectricmaterial because of excessive leakage, as described above. Thus, all ofthese Comparative Examples were not ferroelectric.

Examples 1 and 2 and Examples 4 to 11 with 0.01≦y≦0.05 in the generalformula (1) had particularly high leakage resistance.

Test Example 2

The X-ray diffraction patterns of the piezoelectric elements 300according to Examples 1 to 11 and Comparative Examples 1 to 7 weremeasured at room temperature with an X-ray diffractometer “D8 Discover”manufactured by Bruker AXS using a CuKα line as an X-ray source. An ABO₃peak, a Si substrate peak, a Pt (111) peak, and a Pt (111) CuKβ peakwere observed in all of Examples 1 to 11 and Comparative Examples 1 to7. This result shows that the piezoelectric layers of Examples 1 to 11and Comparative Examples 1 to 7 had an ABO₃ structure. FIGS. 18 and 19show the X-ray diffraction patterns of Examples 4 and 11 and ComparativeExamples 2 and 3, showing the diffraction intensity as a function ofdiffraction angle 2θ. FIG. 20 shows the X-ray diffraction patterns ofExamples 5, 6, and 9. FIG. 19 is an enlarged view of FIG. 18.

FIGS. 18 and 19 show that Example 4 had a diffraction peak at 2θ ofapproximately 46.1°, Comparative Examples 2 and 3 had a diffraction peakat 2θ of approximately 46.5°, and Example 11 had both of thesediffraction peaks. The above-mentioned P-V hystereses show thatComparative Examples 2 and 3 are antiferroelectric, and Example 4 isferroelectric. Thus, the diffraction peak at 2θ=46.5° is assigned to theantiferroelectric phase, and the diffraction peak at 2θ=46.1° isassigned to the ferroelectric phase. These results show that Example 11has a morphotropic phase boundary (MPB) in which the ferroelectricstructure and the antiferroelectric structure coexist. No peak otherthan the substrate and ABO₃ peaks was observed, indicating the absenceof a heterophase.

FIG. 20 shows (Bi_(1−x),La_(x))(Fe_(1−y),Mn_(y))O₃ and Si peaks at2θ=45° to 48°, indicating coexistence of the ferroelectric phase and theantiferroelectric phase in Examples 5, 6, and 9, although the intensityratios of the peaks were different.

The XRD results show that (Bi_(1−x),La_(x))(Fe_(1−y),Mn_(y))O₃ in therange of 0.17≦x≦0.20 had MPB between the antiferroelectric phase and theferroelectric phase.

The area intensity (AF) of a diffraction peak assigned to aferroelectric phase and the area intensity (A_(AF)) of a diffractionpeak assigned to an antiferroelectric phase of the diffraction patternsshown in FIG. 20 were determined by peak fitting with X-ray structureanalysis software Topas 2.1 of Bruker Co. The peak function was PearsonIV. The peak assigned to a ferroelectric phase and the peak assigned toan antiferroelectric phase had the same full width at half maximum(FWHM), which depends on the apparatus and crystallinity. TheA_(AF)/A_(F) ratio was 0.1 for Example 5, 0.5 for Example 6, and 0.9 forExample 9.

Test Example 3

The relationship between electric-field-induced strain and electricfield strength for the piezoelectric elements 300 according to Examples1 to 11 and Comparative Examples 1 to 7 was determined at roomtemperature with a double-beam laser interferometer (DBLI) manufacturedby aixACCT Systems using an electrode pattern of φ=500 μm at a frequencyof 1 kHz. FIGS. 21 to 23 show the results for Examples 4 and 11 andComparative Example 3, and FIGS. 24 to 26 show the results for Examples5, 6, and 9.

FIGS. 21 to 23 show that the displacement at +30 V was 1.10 nm forExample 4, 1.43 nm for Example 11, and 1.72 nm for Comparative Example3. FIG. 19 in Test Example 2 showed that Example 11 had MPB between theantiferroelectric phase and the ferroelectric phase. Accordingly, theelectric-field-induced strain in Example 11 was 1.3 times the strain inExample 4. On the basis of the strain rate normalized to the filmthickness, this corresponds to as high as 0.36%, which is comparable tothe strain rate of PZT practically used. In Examples 4 and 11, theelectric-field-induced strain changed linearly with voltage in the rangeof +30 to −7 V, which is characteristic of a ferroelectric substance.

Comparative Example 3 produced an electric-field-induced strain 1.2times as large as the strain in Example 11. However, Comparative Example3 was an antiferroelectric substance, and therefore had noelectric-field-induced strain in the range of 0 to +10 V and hadinflection in the range of +10 to 0 V.

Thus, in (Bi_(1−x),La_(x))(Fe_(1−y),Mn_(y))O₃, an antiferroelectricsubstance produced the largest electric-field-induced strain. However,in ferroelectric (Bi_(1−x),La_(x)) (Fe_(1−y),Mn_(y))O₃, that is, in therange of 0.10≦x≦0.20 and 0.01≦y≦0.09, the ferroelectric substanceproduced a large electric-field-induced strain comparable to the strainrate of PZT, particularly when the ferroelectric substance approached amorphotropic phase boundary (MPB) between the ferroelectric structureand the antiferroelectric structure, or when x approached 0.17≦x≦0.20 oreven 0.19≦x≦0.20. In addition, unlike the antiferroelectric substance,the piezoelectric strain of the ferroelectric substance changed linearlywith voltage.

FIG. 26 shows that Example 9 had the largest displacement of 1.44 nm at30 V. As shown in FIGS. 24 and 25, Examples 5 and 6 also had a largedisplacement, which was no less than 90% that of Example 9. While thedisplacement increased as the composition approached the composition ofthe antiferroelectric substance, even the displacement of a compositionwith x=0.78 and A_(AF)/A_(F)=0.1 was 90% or more of the displacement ofa composition with x=0.20 and A_(AF)/A_(F)=0.9. Thus, a compositionhaving an intensity ratio A_(AF)/A_(F) of at least approximately 0.1 inXRD can have piezoelectricity comparable to the piezoelectricity of acomposition having an intensity ratio A_(AF)/A_(F) of 0.9.

The second electrode 80, which is the individual electrode of thepiezoelectric element 300, is connected to a lead electrode 90. The leadelectrode 90 may be formed of gold (Au) and extends from theneighborhood of an end of the ink feed channel 14 to the insulator film55.

A protective substrate 30 having a reservoir portion 31, whichconstitutes at least part of a reservoir 100, is attached with anadhesive 35 to the flow-passage-forming substrate 10 on which thepiezoelectric elements 300 are formed, that is, to the first electrode60, the insulator film 55, and the lead electrode 90. The reservoirportion 31 is formed through the protective substrate 30 in thethickness direction and extends in the width direction of thepressure-generating chambers 12. As described above, the reservoirportion 31 communicates with the communication portion 13 in theflow-passage-forming substrate 10, constituting the reservoir 100. Thereservoir 100 serves as a common ink chamber for the pressure-generatingchambers 12. The communication portion 13 in the flow-passage-formingsubstrate 10 may be divided so as to correspond to each of thepressure-generating chambers 12, and only the reservoir portion 31 mayfunction as a reservoir. Furthermore, for example, theflow-passage-forming substrate 10 may only include thepressure-generating chambers 12, and members between theflow-passage-forming substrate 10 and the protective substrate 30 (forexample, the elastic film 50, the insulator film 55, and the like) mayinclude ink feed channels 14 to connect the reservoir with thepressure-generating chambers 12.

A region of the protective substrate 30 opposite the piezoelectricelements 300 includes a piezoelectric-element-holding portion 32, whichhas a space so as not to prevent the displacement of the piezoelectricelements 300. As long as the piezoelectric-element-holding portion 32has a space so as not to prevent the displacement of the piezoelectricelements 300, the space may be sealed or not.

The protective substrate 30 is preferably formed of a material havingsubstantially the same thermal expansion coefficient as theflow-passage-forming substrate 10, for example, a glass or ceramicmaterial. In the present embodiment, the protective substrate 30 isformed of a silicon single crystal, which is the same material as theflow-passage-forming substrate 10.

The protective substrate 30 includes a through-hole 33 passing throughthe protective substrate 30 in the thickness direction. Theneighborhoods of the ends of the lead electrodes 90 extending from thepiezoelectric elements 300 are exposed in the through-hole 33.

A drive circuit 120 for driving the piezoelectric elements 300juxtaposed to each other is fixed onto the protective substrate 30. Thedrive circuit 120 may be a circuit board or a semiconductor integratedcircuit (IC). The drive circuit 120 is electrically connected to thelead electrodes 90 via interconnecting wiring 121 usingelectroconductive wires, such as bonding wires.

The protective substrate 30 is attached to a compliance substrate 40.The compliance substrate 40 includes a sealing film 41 and a fixingsheet 42. The sealing film 41 is formed of a flexible material and sealsone side of the reservoir portion 31. The fixing sheet 42 is formed of arelatively hard material. The fixing sheet 42 has an opening 43 on topof the reservoir 100. Thus, one side of the reservoir 100 is sealed withthe flexible sealing film 41 alone.

In the ink jet print head I according to the present embodiment, thereservoir 100 to the nozzle openings 21 are filled with ink suppliedfrom an ink inlet connected to an external ink supply unit (not shown).A voltage is applied between the first electrode 60 and the secondelectrode 80 on the corresponding pressure-generating chamber 12 inresponse to a print signal from the drive circuit 120 to deform theelastic film 50, the insulator film 55, the first electrode 60, and thepiezoelectric layer 70. The deformation increases the internal pressureof the pressure-generating chamber 12, allowing ink droplets to bedischarged from the corresponding nozzle opening 21.

Other Embodiments

While one embodiment of the invention has been described above, thebasic structure of the invention is not limited to the embodimentdescribed above. For example, although the ABO₃ complex oxide onlycontains Bi, La, Fe, and Mn as metallic elements in the firstembodiment, the ABO₃ complex oxide can further contain another metal toachieve better piezoelectric characteristics.

Although the flow-passage-forming substrate 10 is a silicon singlecrystal substrate in the first embodiment, the flow-passage-formingsubstrate 10 may be an SOI substrate or a glass substrate.

Although the piezoelectric element 300 includes the first electrode 60,the piezoelectric layer 70, and the second electrode 80 on the substrate(the flow-passage-forming substrate 10) in the first embodiment, apiezoelectric material and an electrode-forming material may bealternately stacked to manufacture a longitudinal vibrationpiezoelectric element, which expands and contracts in the axialdirection.

An ink jet print head according to any of the embodiments describedabove can be installed in an ink jet printer as one component of a printhead unit that includes an ink path in communication with an inkcartridge. FIG. 27 is a schematic view of an ink jet printer accordingto an embodiment of the invention.

In an ink jet printer II illustrated in FIG. 27, print head units 1A and1B include the ink jet print head I and house removable cartridges 2Aand 2B. The cartridges 2A and 2B constitute an ink supply unit. Acarriage 3 includes the print head units 1A and 1B and is mounted on acarriage shaft 5 attached to a main body 4 of the printer. The carriage3 can move in the axial direction. For example, the print head units 1Aand 1B discharge a black ink composition and a color ink composition,respectively.

When the driving force of a drive motor 6 is transferred to the carriage3 via a plurality of gears (not shown) and a timing belt 7, the carriage3 including the recording head units 1A and 1B is moved along thecarriage shaft 5. The main body 4 of the printer includes a platen 8along the carriage shaft 5. A recording sheet S, which is a recordingmedium, such as paper, can be fed by a feed roller (not shown) andtransported over the platen 8.

While the ink jet print head has been described as an example of aliquid-ejecting head in the first embodiment, the invention is directedto a wide variety of general liquid-ejecting heads and, as a matter ofcourse, can be applied to liquid-ejecting heads for ejecting liquidother than ink. Examples of other liquid-ejecting heads include printheads for use in image recorders, such as printers,coloring-material-ejecting heads for use in the manufacture of colorfilters for liquid crystal displays, electrode-material-ejecting headsfor use in the formation of electrodes for organic EL displays andfield-emission displays (FED), and bioorganic compound-ejecting headsfor use in the manufacture of biochips.

The invention can be applied not only to piezoelectric elementsinstalled in liquid-ejecting heads, such as ink jet print heads, butalso to piezoelectric elements installed in ultrasonic devices, such asultrasonic transmitters, ultrasonic motors, pressure sensors, andferroelectric memories.

What is claimed is:
 1. A piezoelectric element including a piezoelectriclayer and a plurality of electrodes, wherein the piezoelectric layercontains a complex oxide having the following general formula:(Bi_(1−x),La_(x))(Fe_(1−y),Mn_(y))O₃ (0.10≦x≦0.20, 0.01≦y≦0.09); andwherein the piezoelectric layer undergoes an electric-field-inducedphase transition from an antiferroelectric phase to a ferroelectricphase or phase transition from a ferroelectric phase to anantiferroelectric phase.
 2. The piezoelectric element according to claim1, wherein the x is in the range of 0.17≦x≦0.20.
 3. The piezoelectricelement according to claim 1, wherein the x is in the range of0.19≦x≦0.20.
 4. The piezoelectric element according to claim 1, whereinthe y is in the range of 0.01≦y≦0.05.
 5. An ultrasonic devicecomprising: a piezoelectric element, the piezoelectric element includinga piezoelectric layer and a plurality of electrodes, wherein thepiezoelectric layer contains a complex oxide having the followinggeneral formula:(Bi_(1−x),La_(x))(Fe_(1−y),Mn_(y))O₃ (0.10≦x≦0.20, 0.01≦y≦0.09); andwherein the piezoelectric layer undergoes an electric-field-inducedphase transition from an antiferroelectric phase to a ferroelectricphase or phase transition from a ferroelectric phase to anantiferroelectric phase.
 6. The ultrasonic device according to claim 5,wherein the x is in the range of 0.17≦x≦0.20.
 7. An ultrasonic deviceaccording to claim 5, wherein the x is in the range of 0.19≦x≦0.20. 8.An ultrasonic device according to claim 5, wherein the y is in the rangeof 0.01≦y≦0.05.